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Billy

Billy

Billy is a tiny, visually-oriented programming language for children.

The goal of the project is to create a very small, easy-to-understand set of features which can combine to create complex and fun interactions.

This project was inspired by Isla, a project by Mary Rose Cook.

Please fork to help out, or submit an issue if you find a bug.

Billy is released under the MIT License. See LICENSE.md for details.

Try it out.

The Language

Characters

Characters are represented by geometric shapes, and have attributes.

To make a new character:

[name] is a [type]

where [name] can be any string matching [A-Za-z]+, and [type] is one of: circle, ellipse, oval, square, rectangle, or triangle.

Attributes

Each character has several attributes, which define its appearance.

Each character has attributes x, y, left, right, top, bottom, red, green, blue, radius, size, height, and width.

Expressions

An expression alters a character's attribute. There are two kinds of expressions: 'set' expressions, and 'move' expressions.

'Set' expressions set a characters attribute to a value, and are of the form:

[name]'s [attribute] is [value]

'Move' expressions move a characters attribute by an offset, and are of the form:

move [name]'s [attribute] [offset]

The "'s" can be omitted.

Conditionals

Conditionals allow a user to define interactivity. A user can bind an arbitrary keyboard key to an expression.

when i press [key] [expression]

Once this conditional is created, whenever [key] is pressed, [expression] will be evaluated.

Variables

A variable is a key which is bound to a number. It can be substituted anywhere a number literal is used.

[key] is [value]

Extras

delete [character]
remove [character]

removes a character from the environment

reset

resets the environment, removing all characters, key bindings, and variables

up

minimizes the command prompt

down

maximizes the command prompt

save

saves a screenshot of the canvas

That's it!

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